In agricultural implements, moveable elements are typically covered for safety reasons in order to protect the operator and other persons. However, since the interior of the implements must be accessible for reasons of control and maintenance, the covers are frequently attached to the implement so that they can be removed or pivoted out of the way. In order to prevent accidents, the covers, as a rule, can be opened only by using appropriate tools, with the disadvantage that they cannot be opened without the appropriate tools. If these tools are not available when needed, work on the implement is not possible.
Moreover, it has been proposed that the internal combustion engine of a self propelled agricultural operating machine be stopped automatically when a sensor detects that a cover of the operating machine had been opened (DE 43 09 668 A). Since the cover as well as the internal combustion engine are located on board the self propelled operating machine, the attainment of control is not a problem. Monitoring of the cover is more difficult in the case of implements that are carried or towed by a vehicle, or connected with it by other means and are driven by a power take-off shaft of the vehicle, since the implement would have to be integrated into the control of the vehicle in order to turn off its drive. It has been proposed, for example, to arrange a separate clutch in the drive line of a baler downstream of the power take-off shaft of a tractor, that can be controlled automatically when the covers are in an open condition, as detected by the sensors, so that the driven components of the baler are forcibly retained (DE 101 45 407 A). Here the cost of the additional clutch is seen as a disadvantage.
EP 1 813 146 A describes a combination of a tractor and a baler, each of which is equipped with an electronic control unit. The control units communicate with each other over a bus, so that the control arrangement of the baler can instruct the control arrangement of the tractor to stop in order to wrap and eject the bale. Before the initiation of a baling process the control of the baler brings about the rotation of the power take-off shaft of the tractor.